The genome of the African Green monkey (Cercopithecus aethiops) contains a class of highly repeated DNA. Between 10 and 20 percent of the total genome is made up of repeats (several million) of a family of DNA sequences 172 base pairs long. This family is referred to as alpha-component. A nucleotide sequence corresponding to the most abundant residue at each of the 172 positions in the repeat unit has been determined. The various repeats comprise a set of sequences which vary, in a nonrandom manner, by having alternate base pairs at one or more positions. The alpha-component sequences are organized into nucleosomes in chromatin. The sequence itself does not appear to instruct a unique positioning of the nucleosomal structure.